Badylak seemed to be saying that he could replace human tissue with tissue from another species without triggering a virulent immune response—something that medical scientists considered impossible. Even harder to swallow was the claim that the material could transform, in a matter of months, into whatever type of body tissue had been damaged—muscle, skin, or blood vessel. When Badylak first published his findings, in 1989, the field of regenerative medicine was nonexistent. Badylak’s debut paper on ECM went to press right around the time scientists first coined the term “tissue engineering” to describe what was then considered a small but burgeoning field—the far-out-there efforts to coax cells into tissue to restore, maintain, or improve tissue function or whole organs.
Today, the most widely publicized efforts in the field concentrate on growing tissue outside the body in specially designed, easily controllable “bioreactors.” Badylak’s ECM techniques, however, stimulate the body’s own army of stem cells to do the healing, no external equipment needed. (…)
The discovery that led to this radical approach in wound healing happened quite by accident. It all started with what Badylak’s associates called a “harebrained” idea and a mutt named Rocky. (…)
One afternoon he sedated an affable dog named Rocky, removed part of the animal’s
aorta, and replaced it with a piece of its small intestine, the part of the body that most resembled the tubular structure of Rocky’s blood vessels. Badylak did not expect Rocky to survive the night, but he figured that if the animal had not bled out by morning, it would prove the intestine was sturdy enough to pass blood and hence worthy of further study. This was, Badylak would later admit, the kind of outside-the-box experiment that would probably never get past a university animal-care committee today. (…)
Badylak kept expecting the dog to die, yet every day he would find Rocky healthier and more energetic than the last. Days turned to weeks and Rocky continued to thrive. “I didn’t want to go in surgically and look because I wanted to see how long the intestine would hold,” he says.
Hoping to make sense of his unexpected result, Badylak repeated the procedure on 14 other dogs. They, too, thrived. Six months later he finally operated on one of the dogs to understand why. That, he recalls, is when “things got really weird.” Badylak could
not find the transplanted intestine.
After checking and double-checking to make sure he had the right animal, he placed a piece of tissue culled from the transplant target area under a microscope. What he saw floored him. “I was looking at something that wasn’t supposed to happen,” Badylak says. “It went against everything I had been taught in medical school.” Under the glass he could still see traces of the sutures, but the intestinal tissue was gone. The aorta had grown back in its place. “Nobody would confuse an intestine and an aorta,”
Badylak says. “The microscopic picture is entirely different. I tried to get everybody I could think of to look at it. I kept asking, ‘Am I seeing what I think I’m seeing?’ ” Intestine is composed of soft, smooth, thinly lined walls, with hairlike projections known as villi. Aorta is thick, with the meaty, striated layers of the tissue that characterizes muscle. Badylak examined several other dogs in the weeks that followed and watched the intestinal tissue transform again and again.......